What I did here on my place was water 5 cement bags and let them harden up and then set them where my 18" pipe dumps the water. It has been very effective at dissipating the energy for the last 3 months or so. Only time will tell how it will work long term, but worst case scenario, I am out $15. If you are concerned about the water moving the concrete bags, stick pieces of rebar in the sides as you place them and then water them in place to make them set.

Water dries, rocks crumble, and trees die. The only thing that is eternal is the reputation we leave behind.
- Ancient Viking Proverb